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Deglacial water-table decline in Southern California recorded by noble gas isotopes

TitleDeglacial water-table decline in Southern California recorded by noble gas isotopes
Publication TypeJournal Article
Year of Publication2019
AuthorsSeltzer A.M, Ng J., Danskin W.R, Kulongoski JT, Gannon R.S, Stute M., Severinghaus JP
Date Published2019/12
Type of ArticleArticle
ISBN Number2041-1723
Accession NumberWOS:000502774400001
Keywordsair; climate; diffusion; firn; fractionation; polar ice; Science & Technology - Other Topics

Constraining the magnitude of past hydrological change may improve understanding and predictions of future shifts in water availability. Here we demonstrate that water-table depth, a sensitive indicator of hydroclimate, can be quantitatively reconstructed using Kr and Xe isotopes in groundwater. We present the first-ever measurements of these dissolved noble gas isotopes in groundwater at high precision (<= 0.005 parts per thousand amu(-1); 1 sigma), which reveal depth-proportional signals set by gravitational settling in soil air at the time of recharge. Analyses of California groundwater successfully reproduce modern groundwater levels and indicate a 17.9 +/- 1.3 m (+/- 1 SE) decline in water-table depth in Southern California during the last deglaciation. This hydroclimatic transition from the wetter glacial period to more arid Holocene accompanies a surface warming of 6.2 +/- 0.6 degrees C (+/- 1 SE). This new hydroclimate proxy builds upon an existing paleo-temperature application of noble gases and may identify regions prone to future hydrological change.

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